I believe that when we say much, we are talking about the amount that you spent. When we say many, we are talking about the pieces. So it doesn't matter if how much, or regardless of the note as long as you count the pieces. I chose much because we use the word spend, like it's asking for a price.
How much [money] did you spend?
money - uncountable noun
How many dimes did you spend?
dime- countable noun
That's right, but notice your spelling:
How much money did you spend?
How many mangos did you buy
How much you spend is correct
"How much did you spend?"
You have to use much because there is nothing countable here.
Many can be used when it's clear what you spent:
"How many dollars did you spend?"
You can count the dollars.
"How many hours did it take until it got finished?"
You can count the hours.
P.S: Again: Just my opinion!
Oh, now I see the thread was 1,5 years old...